Electric heater.



UNITED STATES PATENT OFFICE. ELIH U THOMSON, OF SWAMlSUOTTTlll AISSAG/HUSETTS, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

ELECTRIC HEATER.

Specification of Letters Patent.

Patented April 14, 1908.

Application filed October 13, 1906. Serial No. 338,711,

To all whom it may concern:

Be it known that I, ELIHU THOMSON, a

citizen of the United States, residing at- Swampscott, county of Essex, State of Massachusetts, have invented certain new and useful Improvements in Electric Heaters, of which the following is a specification.

This invention relates to electric heaters, and has for its object the provision of means whereby the energy of an electric current may be transformed into heat in a reliable lreep the size of the heater within convenient proportions, and at the same time have suf- -'icient fluid for the necessary insulation, I

provide means for circulating the fluid.

The device to be heated is arranged within the fluid receptacle, so that it will be heated by the circulating fluid. The heating device may be a tubular heater arranged to distribute steam or hot water, the whole constituting a boiler having two circulating systems, one being oil circulated by means of a pump, and the other being water or vapor circulated by gravity or in any other well known manner. I also provide means whereby the temperature may be regulated as, for instance, by cutting out sections of the resistance, as the temperature rises or the steam pressure increases.

Further features of my invention will appear in the course of the following specification, in which I have shown one form of m invention.

eferring to the drawing, 10 is a casing preferably of metal cast into a desired form, although the particular design or method of making the same, forms no part of my in-.

vention. I have shown for purpose of illustration a rectangular watertight casin having an expansion chamber 10, which fill with insulating fiuid 11, such for instance as oil, having a high-flashing point. The heatin resistance 12 is mounted in the casing an immersed in the oil. This resistance may be of any desired type, such for instance as a cast-grid, or a resistance-conductor of any kind. Secured within the not be too sensitive.

- casing is a heat distributing device, comprising a second water-tight casing 13,.provided with tubes 14, constituting a tubular boiler, in which the fluid to be heated circulates around the tubes while the heating medium, in this case the oil, circulates through the tubes. The tubes 15 and 16 furnish respectively an inlet or outlet to the boiler for distributing the hot water or the steam produced in the boiler; One side of the boiler casing 17 is projected downward, so as to cause the liquid to pass to the bottom of the casing as it circulates, and thereby insure that the liquid circulates around the heating resistance.

As a means for circulating the oil or other insulating fluid, I provide a circulating pump in this case, one of the centrifugal type, although any other form of circulating means may be used without departing from the spirit of my invention. I also provide a valve or damper 17 between the inlet and outlet passage of the pump so as to force the oil to pass through the pump, I .use a valve instead of a permanent separating wall so that the heater may be used without the pump if desired, the oil circulating through the tubes by natural circulation.

In order to provide means for regulating the temperature of the heater, I have shown a switch or cut-out controlled by the pressure of steam in'the pipe 16, consisting simply of a cylinder having a plunger 18, acted upon to move the switch 19 against 'the tension of the spring 20. The switch is designed to give a quick break, so that it will This I accomplish by havin springs 21 between the switch arm 19 and the arm 22, upon which the piston rod acts. This particular form of switch I have shown simply for'purposes of illustration. The type of switch will of course depend upon the voltage used and upon other considerations which form no part of my invention. Where very high voltages are used, for instance, it is necessary to have a switch of s ecial construction, while the switch that have shown is adapted for lower voltages. By this construction, a definite pressure must be placed upon the spring before the switch will operate. I have shown the resistance as divided into two sections, in such a manner that the switch arm 19 in the position shown above connects only one section in circuit, while if the contact arm-is moved so as to brid e -the. contacts 23 and 23., both sections will adapted for use with very much lower otenfor it greatly reduces t tials.. The oil makes a very eflicient insulation and the heat is carried away'rapidly as a column of hot oil is displaced by convection and a colder body of oil comes in contact with the resistance continuously. 'The oil circulates through the tubes of the heater although it is within the sec e of my invention to have the liquid circu ate around the tubes instead of through them. The positive-circulation by the means of the pump, formsavery important art of my invention e size of'the heater for a given cagacity, and increases its efficiency. .Very ittle heat is lost durin the transformation, since the casing is jac eted and the oil is kept in circulation. It will be understood of course'that I do not limit my invention to the particular construction or arrangement of parts herein shown and described, but what I have shown is merely for purposes of illustration, since many tacle containin' nit changes and modifications will suggest themselves to those skilled in the art without de-.

parting from the spirit of my invention, the scope of which is set forth in the annexed claims. 4 i

What I claim as new and desire .to secure by Letters Patent of the United States, is;-

1. An electric heater com rising a fluid container and means for circulating the fluid, a resistance conductor "immersed in the fluid, and a heat distributing system receiving its heat from the fluid. r

2. An electric heater comprising a fluid container and means whereby the fluid is caused to circulate, a resistance conductor immersed in the fluid, and a tubular heating device within the container and heated by the fluid.

3. An electric heater comprisin an insulating uid and means for. circ ing the fluid, a resistance a recep- Witnesses:

conductor immersed in the fluid, and a heat distributing system arra ed heat from the circulating uid.

4. An electric heater comprisin a receptacle containing an insulating uid and means for circulati 'the same, a resistance conductor immersed 1n the fluid, and a tubular heating device within the container adapted to be heated by the circulation of the fluid.

5. An electric heater comprisin a receptacle, containing oil having a higl flashing point and means for circulating t e same, a resistance conductor immersed in the oil and tem partially within the container and aring oil.

6. An electric heater comprising tacle containing oil having a hi flashing point and means for circulating e same, a resistance conductor immersed 1n the oil and adapted to heat the same, and a tubular heatin device within the container for a eat distributin medium.

-7. An electric'ieater corn rising a fluid container and means for circu ating the fluid, a resistance conductor immersedin the fluid, a heat distributing device within the container, and means controlled by said device for varyin the resistance.

8. An e ectric heater compribing a receptacle, an insulating fluid and means for circulating the fluid, a heating resistance 1mmersed in the fluid, a heat-distributing de-' vice within the receptacle, and means cona receptacle containing oil having a big flashing point, means for circulati the same, a heatmg resistance imniersedin t e 011 andadapted to heat the same, a tubular heater within the container, and means controlled thereby for varying the heating resistance.

In witness whereof, I have hereunto set my hand this twentv-fifth dav of September, 1906.

' ELIHU THOMSON.

JOHN A. MCMANUS, Jr.,- HENRY O.'WnsTnNnARP.

to receive its ranged to receive its heat from the circulattrolled by said device for varying said re-' sistance. a i

- 9. An. electric heater comprism a recepadapted to heat the same, and a heating sys- I heating 

